The effect of aqueous extract of Tamarindus indica
(AETI) was studied on the guinea pig taenia coli, due to its use for treatment of constipation in traditional medicines. AETI, at concentrations ranging from 10-8
mg/ml to 10-2
mg/ml, increased the spontaneous contractile activity of guinea pig taenia coli in a dose-dependent manner (EC50= 4x10-6
mg/ml). This activity was unaffected by atropine. In high K+
-free solution containing EDTA, AETI as well as acetylcholine, used as a control, induced tonic contraction. These results suggest that the plant extract exert a spasmogenic effect that would not involve cholinergic mechanism of action. However, these active principles could mobilize both extra cellular calcium and intracellular calcium from internal stores.